Groundwater contamination by pesticides and other organic
compounds is a widespread problem in rural midwestern states, especially in
areas of intensive agriculture and shallow or sandy soils. Detection of
groundwater pollution using analytical methods is well documented, but its
effects are not well known. To assess the acceptability of well water for human
consumption, scientists usually analyze samples for chemicals such as
hydrocarbons and fertilizer and pesticide residues and review toxicity-testi ng
information--mostly on laboratory rodent species--to estimate aggregate risks.
This approach is slow, expensive and unable to account for additive,
offsetting, synergistic or antagonistic effects of mixtures of trace chemicals
commonly encountered in d rinking water. This problem is compounded by the fact
that most contaminants exist in groundwater at concentrations below those
detectable by inexpensive analytical methods. Analytical scans with state-of-the-art
instrumentation needed for low-level analy sis are cost-prohibitive for the
typical groundwater user. There is a need to employ new cost-effective
assessment tools that directly measure potential health effects of ambient
levels of contaminants in groundwater. This approach has been successfully a
pplied to detect toxins found in surface water and written into
permit-compliance monitoring protocols in many states. Biomonitoring or
toxicity testing is an established screening tool that can be used directly to
assess the outcome of complex contaminan t interactions in water samples, but
this approach has yet to be applied in a systematic manner to the
identification of potential hazards from exposure to groundwater pollution.
Measurements of toxicity are not intended to replace chemical quantification
methods. However, they can make better use of analytical time by screening
samples for biological effects and using that information to prioritize samples
for more expensive chemical testing.

Statement of results and benefits:

Contaminant sorbents e.g. semipermeable membrane devices
(SPMDs), C 18 reverse-phase Sep-pak solid-phase extraction
cartridges, and copper phthalocyanine trisulfonate covalently linked to
cellulose or blue rayon] will be deployed at known co ntaminated groundwater
sites, using traps immersed in existing monitoring wells. After sufficient time
to accrue contaminants, the sorbents will be removed, and the sorbates
extracted, concentrated and analyzed for toxicity using variants of
submitochrond rial (SMP) and bacterial photoluminescence Microtox bioassays.
Chemical analyses will be performed only on particularly toxic samples or to
supplement existing water quality data from monitoring wells.

Primary beneficiaries of this research will be farming
families and populations of small rural communities--the people most directly
affected by groundwater tainted by toxic residues of agricultural chemicals,
the solvents used in their formulation, an d petroleum-based fuels. These people
have no quick and inexpensive means for testing their water supplies to ensure
safe potability. Most present-day tests examine samples for only one compound
or class of compounds at a time, and are costly and time-con suming. It is
often weeks before analytical results become available, and these reveal only
one-time snapshots of the water quality and, while bioassay results of toxicant
mixtures collected long-term on selective sorbents provide estimates of
aggregate t oxicity. Regulators and consulting engineering companies performing
site evaluations would similarly benefit, as these techniques promise to
provide an excellent screening tool for prioritizing samples or sites for more
extensive and costly chemical analy sis.